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A hypothalamomedullary network for physiological responses to environmental stresses. Nat Rev Neurosci 2021; 23:35-52. [PMID: 34728833 DOI: 10.1038/s41583-021-00532-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2021] [Indexed: 02/07/2023]
Abstract
Various environmental stressors, such as extreme temperatures (hot and cold), pathogens, predators and insufficient food, can threaten life. Remarkable progress has recently been made in understanding the central circuit mechanisms of physiological responses to such stressors. A hypothalamomedullary neural pathway from the dorsomedial hypothalamus (DMH) to the rostral medullary raphe region (rMR) regulates sympathetic outflows to effector organs for homeostasis. Thermal and infection stress inputs to the preoptic area dynamically alter the DMH → rMR transmission to elicit thermoregulatory, febrile and cardiovascular responses. Psychological stress signalling from a ventromedial prefrontal cortical area to the DMH drives sympathetic and behavioural responses for stress coping, representing a psychosomatic connection from the corticolimbic emotion circuit to the autonomic and somatic motor systems. Under starvation stress, medullary reticular neurons activated by hunger signalling from the hypothalamus suppress thermogenic drive from the rMR for energy saving and prime mastication to promote food intake. This Perspective presents a combined neural network for environmental stress responses, providing insights into the central circuit mechanism for the integrative regulation of systemic organs.
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Hemodynamics in acute stroke: Cerebral and cardiac complications. HANDBOOK OF CLINICAL NEUROLOGY 2021; 177:295-317. [PMID: 33632449 DOI: 10.1016/b978-0-12-819814-8.00015-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Hemodynamics is the study of blood flow, where parameters have been defined to quantify blood flow and the relationship with systemic circulatory changes. Understanding these perfusion parameters, the relationship between different blood flow variables and the implications for ischemic injury are outlined in the ensuing discussion. This chapter focuses on the hemodynamic changes that occur in ischemic stroke, and their contribution to ischemic stroke pathophysiology. We discuss the interaction between cardiovascular response and hemodynamic changes in stroke. Studying hemodynamic changes has a key role in stroke prevention, therapeutic implications and prognostic importance in acute ischemic stroke: preexisting hemodynamic and autoregulatory impairments predict the occurrence of stroke. Hemodynamic failure predisposes to the formation of thromboemboli and accelerates infarction due to impairing compensatory mechanisms. In ischemic stroke involving occlusion of a large vessel, persistent collateral circulation leads to preservation of ischemic penumbra and therefore justifying endovascular thrombectomy. Following thrombectomy, impaired autoregulation may lead to reperfusion injury and hemorrhage.
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Tan CL, Knight ZA. Regulation of Body Temperature by the Nervous System. Neuron 2019; 98:31-48. [PMID: 29621489 DOI: 10.1016/j.neuron.2018.02.022] [Citation(s) in RCA: 291] [Impact Index Per Article: 58.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 02/19/2018] [Accepted: 02/23/2018] [Indexed: 01/24/2023]
Abstract
The regulation of body temperature is one of the most critical functions of the nervous system. Here we review our current understanding of thermoregulation in mammals. We outline the molecules and cells that measure body temperature in the periphery, the neural pathways that communicate this information to the brain, and the central circuits that coordinate the homeostatic response. We also discuss some of the key unresolved issues in this field, including the following: the role of temperature sensing in the brain, the molecular identity of the warm sensor, the central representation of the labeled line for cold, and the neural substrates of thermoregulatory behavior. We suggest that approaches for molecularly defined circuit analysis will provide new insight into these topics in the near future.
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Affiliation(s)
- Chan Lek Tan
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158
| | - Zachary A Knight
- Department of Physiology, University of California, San Francisco, San Francisco, CA 94158; Kavli Center for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94158; Neuroscience Graduate Program, University of California, San Francisco, San Francisco, CA 94158.
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4
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Abstract
Maintenance of a homeostatic body core temperature is a critical brain function accomplished by a central neural network. This orchestrates a complex behavioral and autonomic repertoire in response to environmental temperature challenges or declining energy homeostasis and in support of immune responses and many behavioral states. This review summarizes the anatomical, neurotransmitter, and functional relationships within the central neural network that controls the principal thermoeffectors: cutaneous vasoconstriction regulating heat loss and shivering and brown adipose tissue for heat production. The core thermoregulatory network regulating these thermoeffectors consists of parallel but distinct central efferent pathways that share a common peripheral thermal sensory input. Delineating the neural circuit mechanism underlying central thermoregulation provides a useful platform for exploring its functional organization, elucidating the molecular underpinnings of its neuronal interactions, and discovering novel therapeutic approaches to modulating body temperature and energy homeostasis.
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Affiliation(s)
- S F Morrison
- Department of Neurological Surgery, Oregon Health and Science University, Portland, Oregon 97239, USA;
| | - K Nakamura
- Department of Integrative Physiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
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5
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Qureshi AI, Qureshi MH. Acute hypertensive response in patients with intracerebral hemorrhage pathophysiology and treatment. J Cereb Blood Flow Metab 2018; 38:1551-1563. [PMID: 28812942 PMCID: PMC6125978 DOI: 10.1177/0271678x17725431] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Acute hypertensive response is a common systemic response to occurrence of intracerebral hemorrhage which has gained unique prominence due to high prevalence and association with hematoma expansion and increased mortality. Presumably, the higher systemic blood pressure predisposes to continued intraparenchymal hemorrhage by transmission of higher pressure to the damaged small arteries and may interact with hemostatic and inflammatory pathways. Therefore, intensive reduction of systolic blood pressure has been evaluated in several clinical trials as a strategy to reduce hematoma expansion and subsequent death and disability. These trials have demonstrated either a small magnitude benefit (second intensive blood pressure reduction in acute cerebral hemorrhage trial and efficacy of nitric oxide in stroke trial) or no benefit (antihypertensive treatment of acute cerebral hemorrhage 2 trial) with intensive systolic blood pressure reduction compared with modest or standard blood pressure reduction. The differences may be explained by the variation in intensity of systolic blood pressure reduction between trials. A treatment threshold of systolic blood pressure of ≥180 mm with the target goal of systolic blood pressure reduction to values between 130 and 150 mm Hg within 6 h of symptom onset may be best supported by current evidence.
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Abstract
Body core temperature of mammals is regulated by the central nervous system, in which the preoptic area (POA) of the hypothalamus plays a pivotal role. The POA receives peripheral and central thermosensory neural information and provides command signals to effector organs to elicit involuntary thermoregulatory responses, including shivering thermogenesis, nonshivering brown adipose tissue thermogenesis, and cutaneous vasoconstriction. Cool-sensory and warm-sensory signals from cutaneous thermoreceptors, monitoring environmental temperature, are separately transmitted through the spinal-parabrachial-POA neural pathways, distinct from the spinothalamocortical pathway for perception of skin temperature. These cutaneous thermosensory inputs to the POA likely impinge on warm-sensitive POA neurons, which monitor body core (brain) temperature, to alter thermoregulatory command outflows from the POA. The cutaneous thermosensory afferents elicit rapid thermoregulatory responses to environmental thermal challenges before they impact body core temperature. Peripheral humoral signals also act on neurons in the POA to transmit afferent information of systemic infection and energy storage to induce fever and to regulate energy balance, respectively. This chapter describes the thermoregulatory afferent mechanisms that convey cutaneous thermosensory signals to the POA and that integrate the neural and humoral afferent inputs to the POA to provide descending command signals to thermoregulatory effectors.
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Affiliation(s)
- Kazuhiro Nakamura
- Department of Integrative Physiology, Nagoya University Graduate School of Medicine, Nagoya, Japan.
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7
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Morrison SF. Efferent neural pathways for the control of brown adipose tissue thermogenesis and shivering. HANDBOOK OF CLINICAL NEUROLOGY 2018; 156:281-303. [PMID: 30454595 DOI: 10.1016/b978-0-444-63912-7.00017-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The fundamental central neural circuits for thermoregulation orchestrate behavioral and autonomic repertoires that maintain body core temperature during thermal challenges that arise from either the ambient or the internal environment. This review summarizes our understanding of the neural pathways within the fundamental thermoregulatory reflex circuitry that comprise the efferent (i.e., beyond thermosensory) control of brown adipose tissue (BAT) and shivering thermogenesis: the motor neuron systems consisting of the BAT sympathetic preganglionic neurons and BAT sympathetic ganglion cells, and the alpha- and gamma-motoneurons; the premotor neurons in the region of the rostral raphe pallidus, and the thermogenesis-promoting neurons in the dorsomedial hypothalamus/dorsal hypothalamic area. Also included are inputs to, and neurochemical modulators of, these efferent neuronal populations that could influence their activity during thermoregulatory responses. Signals of metabolic status can be particularly significant for the energy-hungry thermoeffectors for heat production.
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Affiliation(s)
- Shaun F Morrison
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR, United States.
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Central regulation of brown adipose tissue thermogenesis and energy homeostasis dependent on food availability. Pflugers Arch 2017; 470:823-837. [PMID: 29209779 PMCID: PMC5942360 DOI: 10.1007/s00424-017-2090-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 11/17/2017] [Accepted: 11/20/2017] [Indexed: 12/19/2022]
Abstract
Energy homeostasis of mammals is maintained by balancing energy expenditure within the body and energy intake through feeding. Several lines of evidence indicate that brown adipose tissue (BAT), a sympathetically activated thermogenic organ, turns excess energy into heat to maintain the energy balance in rodents and humans, in addition to its thermoregulatory role for the defense of body core temperature in cold environments. Elucidating the central circuit mechanism controlling BAT thermogenesis dependent on nutritional conditions and food availability in relation to energy homeostasis is essential to understand the etiology of symptoms caused by energy imbalance, such as obesity. The central thermogenic command outflow to BAT descends through an excitatory neural pathway mediated by hypothalamic, medullary and spinal sites. This sympathoexcitatory thermogenic drive is controlled by tonic GABAergic inhibitory signaling from the thermoregulatory center in the preoptic area, whose tone is altered by body core and cutaneous thermosensory inputs. This circuit controlling BAT thermogenesis for cold defense also functions for the development of fever and psychological stress-induced hyperthermia, indicating its important role in the defense from a variety of environmental stressors. When food is unavailable, hunger-driven neural signaling from the hypothalamus activates GABAergic neurons in the medullary reticular formation, which then block the sympathoexcitatory thermogenic outflow to BAT to reduce energy expenditure and simultaneously command the masticatory motor system to promote food intake—effectively commanding responses to survive starvation. This article reviews the central mechanism controlling BAT thermogenesis in relation to the regulation of energy and thermal homeostasis dependent on food availability.
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Majidi S, Suarez JI, Qureshi AI. Management of Acute Hypertensive Response in Intracerebral Hemorrhage Patients After ATACH-2 Trial. Neurocrit Care 2016; 27:249-258. [DOI: 10.1007/s12028-016-0341-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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El Bitar N, Pollin B, Karroum E, Pincedé I, Le Bars D. Entanglement between thermoregulation and nociception in the rat: the case of morphine. J Neurophysiol 2016; 116:2473-2496. [PMID: 27605533 PMCID: PMC5133307 DOI: 10.1152/jn.00482.2016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 09/03/2016] [Indexed: 11/22/2022] Open
Abstract
In thermoneutral conditions, rats display cyclic variations of the vasomotion of the tail and paws, the most widely used target organs in current acute or chronic animal models of pain. Systemic morphine elicits their vasoconstriction followed by hyperthermia in a naloxone-reversible and dose-dependent fashion. The dose-response curves were steep with ED50 in the 0.5-1 mg/kg range. Given the pivotal functional role of the rostral ventromedial medulla (RVM) in nociception and the rostral medullary raphe (rMR) in thermoregulation, two largely overlapping brain regions, the RVM/rMR was blocked by muscimol: it suppressed the effects of morphine. "On-" and "off-" neurons recorded in the RVM/rMR are activated and inhibited by thermal nociceptive stimuli, respectively. They are also implicated in regulating the cyclic variations of the vasomotion of the tail and paws seen in thermoneutral conditions. Morphine elicited abrupt inhibition and activation of the firing of on- and off-cells recorded in the RVM/rMR. By using a model that takes into account the power of the radiant heat source, initial skin temperature, core body temperature, and peripheral nerve conduction distance, one can argue that the morphine-induced increase of reaction time is mainly related to the morphine-induced vasoconstriction. This statement was confirmed by analyzing in psychophysical terms the tail-flick response to random variations of noxious radiant heat. Although the increase of a reaction time to radiant heat is generally interpreted in terms of analgesia, the present data question the validity of using such an approach to build a pain index.
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Affiliation(s)
- Nabil El Bitar
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Bernard Pollin
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Elias Karroum
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Ivanne Pincedé
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Daniel Le Bars
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; and
- Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
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Kvistad CE, Oygarden H, Logallo N, Thomassen L, Waje-Andreassen U, Moen G, Naess H. A stress-related explanation to the increased blood pressure and its course following ischemic stroke. Vasc Health Risk Manag 2016; 12:435-442. [PMID: 27956837 PMCID: PMC5113932 DOI: 10.2147/vhrm.s109032] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background A hypertensive response after ischemic stroke is frequent, yet its pathophysiology is unknown. Mechanisms related to local ischemic damage, major vascular occlusion, and psychological stress due to acute illness have been proposed. We assessed the natural course of blood pressure (BP) within the first 24 h in groups of ischemic stroke patients with different characteristics. We hypothesized that a consistent BP reduction, regardless of stroke location, time window from debut to admission and presence of persistent vascular occlusion, would favor a stress-related mechanism as an important cause of the hypertensive response after ischemic stroke. Methods Ischemic stroke patients (n=1067) were prospectively registered, and BP was measured on admission and <3 h, 3–6 h, 6–12 h and 12–24 h after admission. Patients were categorized according to the location of diffusion-weighted imaging (DWI) lesions (cortical, large subcortical, mixed cortico-subcortical, lacunar, cerebellar, brain stem or multiple), time window (admitted within or after 6 h of symptom onset) and presence of persistent proximal middle cerebral artery (MCA) occlusion versus normal findings on magnetic resonance angiography (MRA) at 24 h. Results A reduction in systolic BP and diastolic BP from baseline to 12–24 h was found across all DWI locations except for diastolic BP in cerebellar (P=0.072) lesions. Apart from diastolic BP in patients with normal MRA findings at 24 h (P=0.060), a significant fall in systolic BP and diastolic BP at 12–24 h was registered, irrespective of whether patients were admitted within 6 h or after 6 h of stroke onset or had persistent MCA occlusion versus normal MRA findings. Conclusion We found a relatively consistent decline in BP within 24 h after admission across different stroke locations in patients admitted within or after 6 h of stroke onset and in patients with persistent MCA occlusion. Our findings suggest that a systemic factor such as psychological stress may be an important contributor to the frequently elevated BP on admission in patients with ischemic stroke.
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Affiliation(s)
| | - Halvor Oygarden
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - Nicola Logallo
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - Lars Thomassen
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | | | - Gunnar Moen
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - Halvor Naess
- Department of Neurology, Haukeland University Hospital, Bergen, Norway
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Nam H, Kerman IA. Distribution of catecholaminergic presympathetic-premotor neurons in the rat lower brainstem. Neuroscience 2016; 324:430-45. [PMID: 26946268 DOI: 10.1016/j.neuroscience.2016.02.066] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Revised: 02/11/2016] [Accepted: 02/26/2016] [Indexed: 11/15/2022]
Abstract
We previously characterized the organization of presympathetic-premotor neurons (PSPMNs), which send descending poly-synaptic projections with collaterals to skeletal muscle and the adrenal gland. Such neurons may play a role in shaping integrated adaptive responses, and many of them were found within well-characterized regions of noradrenergic cell populations suggesting that some of the PSPMNs are catecholaminergic. To address this issue, we used retrograde trans-synaptic tract-tracing with attenuated pseudorabies virus (PRV) recombinants combined with multi-label immunofluorescence to identify PSPMNs expressing tyrosine hydroxylase (TH). Our findings indicate that TH-immunoreactive (ir) PSPMNs are present throughout the brainstem within multiple cell populations, including the A1, C1, C2, C3, A5 and A7 cell groups along with the locus coeruleus (LC) and the nucleus subcoeruleus (SubC). The largest numbers of TH-ir PSPMNs were located within the LC and SubC. Within SubC and the A7 cell group, about 70% of TH-ir neurons were PSPMNs, which was a significantly greater fraction of neurons than in the other brain regions we examined. These findings indicate that TH-ir neurons near the pontomesencephalic junction that are distributed across the LC, SubC, and the A7 may play a prominent role in somatomotor-sympathetic integration, and that the major functional role of the A7 and SubC noradrenergic cell groups maybe in the coordination of concomitant activation of somatomotor and sympathetic outflows. These neurons may participate in mediating homeostatic adaptations that require simultaneous activation of sympathetic and somatomotor nerves in the periphery.
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Affiliation(s)
- H Nam
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, United States; Cell Molecular and Developmental Biology Theme, Graduate Biomedical Sciences Program, University of Alabama at Birmingham, Birmingham, AL, United States
| | - I A Kerman
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, United States.
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Morrison SF. Central neural control of thermoregulation and brown adipose tissue. Auton Neurosci 2016; 196:14-24. [PMID: 26924538 DOI: 10.1016/j.autneu.2016.02.010] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 02/05/2016] [Accepted: 02/19/2016] [Indexed: 12/26/2022]
Abstract
Central neural circuits orchestrate the homeostatic repertoire that maintains body temperature during environmental temperature challenges and alters body temperature during the inflammatory response. This review summarizes the experimental underpinnings of our current model of the CNS pathways controlling the principal thermoeffectors for body temperature regulation: cutaneous vasoconstriction controlling heat loss, and shivering and brown adipose tissue for thermogenesis. The activation of these effectors is regulated by parallel but distinct, effector-specific, core efferent pathways within the CNS that share a common peripheral thermal sensory input. Via the lateral parabrachial nucleus, skin thermal afferent input reaches the hypothalamic preoptic area to inhibit warm-sensitive, inhibitory output neurons which control heat production by inhibiting thermogenesis-promoting neurons in the dorsomedial hypothalamus that project to thermogenesis-controlling premotor neurons in the rostral ventromedial medulla, including the raphe pallidus, that descend to provide the excitation of spinal circuits necessary to drive thermogenic thermal effectors. A distinct population of warm-sensitive preoptic neurons controls heat loss through an inhibitory input to raphe pallidus sympathetic premotor neurons controlling cutaneous vasoconstriction. The model proposed for central thermoregulatory control provides a useful platform for further understanding of the functional organization of central thermoregulation and elucidating the hypothalamic circuitry and neurotransmitters involved in body temperature regulation.
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Affiliation(s)
- Shaun F Morrison
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR 97239, Unites States.
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14
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El Bitar N, Pollin B, Huang G, Mouraux A, Le Bars D. The rostral ventromedial medulla control of cutaneous vasomotion of paws and tail in the rat: implication for pain studies. J Neurophysiol 2015; 115:773-89. [PMID: 26581872 DOI: 10.1152/jn.00695.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 10/13/2015] [Indexed: 11/22/2022] Open
Abstract
Thermal neutrality in rodents is achieved by large cyclic variations of the sympathetic drive of the vasomotion of the tail and paws, the most widely used target organs in current acute or chronic animal models of pain. Given the pivotal functional role of rostral ventromedial medulla (RVM) in nociception and rostral medullary raphe (rMR) in thermoregulation, two largely overlapping brain regions, we aimed at circumscribing the brainstem regions that are the source of premotor afferents to sympathetic preganglionic neurons that control the vasomotor tone of the tail and hind paws. A thermometric infrared camera recorded indirectly the vasomotor tone of the tail and hind paws. During the control period, the rat was maintained in vasoconstriction by preserving a stable, homogeneous, and constant surrounding temperature, slightly below the core temperature. The functional blockade of the RVM/rMR by the GABAA receptor agonist muscimol (0.5 nmol, 50 nl) elicited an extensive increase of the temperature of the paws and tail, associated with a slight decrease of blood pressure and heart rate. Both the increased heat loss through vasodilatation and the decrease heart-induced heat production elicited a remarkable reduction of the central temperature. The effective zones were circumscribed to the parts of the RVM/rMR facing the facial nucleus. They match very exactly the brain regions often described as specifically devoted to the control of nociception. Our data support and urge on the highest cautiousness regarding the interpretation of results aimed at studying the effects of any pharmacological manipulations of RVM/rMR with the usual tests of pain.
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Affiliation(s)
- Nabil El Bitar
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France; and
| | - Bernard Pollin
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France; and
| | - Gan Huang
- Institute of Neuroscience, Université Catholique de Louvain, Brussels, Belgium
| | - André Mouraux
- Institute of Neuroscience, Université Catholique de Louvain, Brussels, Belgium
| | - Daniel Le Bars
- Sorbonne Universités, Université Pierre et Marie Curie, Faculté de Médecine, Paris, France; Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France; and
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15
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Abstract
Whether there are any benefits without harm from early lowering of blood pressure (BP) in the setting of acute ischemic stroke (AIS) has been a longstanding controversy in medicine. Whilst most studies have consistently shown associations between elevated BP, particularly systolic BP, and poor outcome, some also report that very low BP (systolic <130 mmHg) and large reductions in systolic BP are associated with poor outcomes in AIS. However, despite these associations, the observed U- or J-shaped relationship between BP and outcome in these patients may not be causally related. Patients with more severe strokes may have a more prominent autonomic response and later lower BP as their condition worsens, often pre-terminally. Fortunately, substantial progress has been made in recent years with new evidence arising from well-conducted randomized trials. This review outlines new evidence and recommendations for clinical practice over BP management in AIS.
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Affiliation(s)
- Cheryl Carcel
- The George Institute for Global Health, Sydney, Australia
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Abstract
The heat shock response (HSR) is an ancient and highly conserved process that is essential for coping with environmental stresses, including extremes of temperature. Fever is a more recently evolved response, during which organisms temporarily subject themselves to thermal stress in the face of infections. We review the phylogenetically conserved mechanisms that regulate fever and discuss the effects that febrile-range temperatures have on multiple biological processes involved in host defense and cell death and survival, including the HSR and its implications for patients with severe sepsis, trauma, and other acute systemic inflammatory states. Heat shock factor-1, a heat-induced transcriptional enhancer is not only the central regulator of the HSR but also regulates expression of pivotal cytokines and early response genes. Febrile-range temperatures exert additional immunomodulatory effects by activating mitogen-activated protein kinase cascades and accelerating apoptosis in some cell types. This results in accelerated pathogen clearance, but increased collateral tissue injury, thus the net effect of exposure to febrile range temperature depends in part on the site and nature of the pathologic process and the specific treatment provided.
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Affiliation(s)
- Jeffrey D Hasday
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Maryland School of Medicine and the Baltimore V.A. Medical Center, Baltimore, Maryland
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17
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El Bitar N, Pollin B, Le Bars D. "On-" and "off-" cells in the rostral ventromedial medulla of rats held in thermoneutral conditions: are they involved in thermoregulation? J Neurophysiol 2014; 112:2199-217. [PMID: 25008415 DOI: 10.1152/jn.00722.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In thermal neutral condition, rats display cyclic variations of the vasomotion of the tail and paws, synchronized with fluctuations of blood pressure, heart rate, and core body temperature. "On-" and "off-" cells located in the rostral ventromedial medulla, a cerebral structure implicated in somatic sympathetic drive, 1) exhibit similar spontaneous cyclic activities in antiphase and 2) are activated and inhibited by thermal nociceptive stimuli, respectively. We aimed at evaluating the implication of such neurons in autonomic regulation by establishing correlations between their firing and blood pressure, heart rate, and skin and core body temperature variations. When, during a cycle, a relative high core body temperature was reached, the on-cells were activated and within half a minute, the off-cells and blood pressure were depressed, followed by heart rate depression within a further minute; vasodilatation of the tail followed invariably within ∼3 min, often completed with vasodilatation of hind paws. The outcome was an increased heat loss that lessened the core body temperature. When the decrease of core body temperature achieved a few tenths of degrees, sympathetic activation switches off and converse variations occurred, providing cycles of three to seven periods/h. On- and off-cell activities were correlated with inhibition and activation of the sympathetic system, respectively. The temporal sequence of events was as follows: core body temperature → on-cell → off-cell ∼ blood pressure → heart rate → skin temperature → core body temperature. The function of on- and off-cells in nociception should be reexamined, taking into account their correlation with autonomic regulations.
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Affiliation(s)
- Nabil El Bitar
- Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, Faculté de Médecine, Paris, France; and Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Bernard Pollin
- Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, Faculté de Médecine, Paris, France; and Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
| | - Daniel Le Bars
- Sorbonne Universités, Université Pierre et Marie Curie, Université Paris 06, Faculté de Médecine, Paris, France; and Neurosciences Paris-Seine, Institut National de la Santé et de la Recherche Médicale UMRS-1130, Centre National de la Recherche Scientifique UMR-8246, Paris, France
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Hossaini M, Goos JAC, Kohli SK, Holstege JC. Distribution of glycine/GABA neurons in the ventromedial medulla with descending spinal projections and evidence for an ascending glycine/GABA projection. PLoS One 2012; 7:e35293. [PMID: 22558137 PMCID: PMC3340372 DOI: 10.1371/journal.pone.0035293] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 03/14/2012] [Indexed: 11/23/2022] Open
Abstract
The ventromedial medulla (VM), subdivided in a rostral (RVM) and a caudal (CVM) part, has a powerful influence on the spinal cord. In this study, we have identified the distribution of glycine and GABA containing neurons in the VM with projections to the cervical spinal cord, the lumbar dorsal horn, and the lumbar ventral horn. For this purpose, we have combined retrograde tracing using fluorescent microspheres with fluorescent in situ hybridization (FISH) for glycine transporter 2 (GlyT2) and GAD67 mRNAs to identify glycinergic and/or GABAergic (Gly/GABA) neurons. Since the results obtained with FISH for GlyT2, GAD67, or GlyT2 + GAD67 mRNAs were not significantly different, we concluded that glycine and GABA coexisted in the various projection neurons. After injections in the cervical cord, we found that 29% ± 1 (SEM) of the retrogradely labeled neurons in the VM were Gly/GABA (RVM: 43%; CVM: 21%). After lumbar dorsal horn injections 31% ± 3 of the VM neurons were Gly/GABA (RVM: 45%; CVM: 12%), and after lumbar ventral horn injections 25% ± 2 were Gly/GABA (RVM: 35%; CVM: 17%). In addition, we have identified a novel ascending Gly/GABA pathway originating from neurons in the area around the central canal (CC) throughout the spinal cord and projecting to the RVM, emphasizing the interaction between the ventromedial medulla and the spinal cord. The present study has now firmly established that GABA and glycine are present in many VM neurons that project to the spinal cord. These neurons strongly influence spinal processing, most notably the inhibition of nociceptive transmission.
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Affiliation(s)
- Mehdi Hossaini
- Department of Neuroscience, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Jacqueline A. C. Goos
- Department of Neuroscience, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Somesh K. Kohli
- Department of Neuroscience, Erasmus University Medical Center, Rotterdam, The Netherlands
| | - Jan C. Holstege
- Department of Neuroscience, Erasmus University Medical Center, Rotterdam, The Netherlands
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Luong L, Carrive P. Orexin microinjection in the medullary raphe increases heart rate and arterial pressure but does not reduce tail skin blood flow in the awake rat. Neuroscience 2012; 202:209-17. [DOI: 10.1016/j.neuroscience.2011.11.073] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Revised: 11/29/2011] [Accepted: 11/30/2011] [Indexed: 01/14/2023]
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20
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Kelly KJ, Donner NC, Hale MW, Lowry CA. Swim stress activates serotonergic and nonserotonergic neurons in specific subdivisions of the rat dorsal raphe nucleus in a temperature-dependent manner. Neuroscience 2011; 197:251-68. [PMID: 21945646 DOI: 10.1016/j.neuroscience.2011.09.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 09/03/2011] [Accepted: 09/06/2011] [Indexed: 11/18/2022]
Abstract
Physical (exteroceptive) stimuli and emotional (interoceptive) stimuli are thought to influence stress-related physiologic and behavioral responses through different neural mechanisms. Previous studies have demonstrated that stress-induced activation of brainstem serotonergic systems is influenced by environmental factors such as temperature. In order to further investigate the effects of environmental influences on stress-induced activation of serotonergic systems, we exposed adult male Wistar rats to either home cage control conditions or a 15-min swim in water maintained at 19 °C, 25 °C, or 35 °C and conducted dual immunohistochemical staining for c-Fos, a marker of immediate-early nuclear activation, and tryptophan hydroxylase (TPH), a marker of serotonergic neurons. Changes in core body temperature were documented using biotelemetry. As expected, exposure to cold (19 °C) swim, relative to warm (35 °C) swim, increased c-Fos expression in the external lateral part of the parabrachial nucleus (LPBel), an important part of the spinoparabrachial pathway involved in sensation of cold, cutaneous stimuli, and in serotonergic neurons in the raphe pallidus nucleus (RPa), an important part of the efferent mechanisms controlling thermoregulatory warming responses. In addition, exposure to cold (19 °C) swim, relative to 35 °C swim, increased c-Fos expression in the dorsal raphe nucleus, ventrolateral part/periaqueductal gray (DRVL/VLPAG) and dorsal raphe nucleus, interfascicular part (DRI). Both of these subregions of the dorsal raphe nucleus (DR) have previously been implicated in thermoregulatory responses. Altogether, the data are consistent with the hypothesis that midbrain serotonergic neurons, possibly via activation of afferents to the DR by thermosensitive spinoparabrachial pathways, play a role in integration of physiologic and behavioral responses to interoceptive stress-related cues involved in forced swimming and exteroceptive cues related to cold ambient temperature.
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Affiliation(s)
- K J Kelly
- Department of Integrative Physiology and Center for Neuroscience, University of Colorado Boulder, Boulder, CO 80309-0354, USA.
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21
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Nakamura K. Central circuitries for body temperature regulation and fever. Am J Physiol Regul Integr Comp Physiol 2011; 301:R1207-28. [PMID: 21900642 DOI: 10.1152/ajpregu.00109.2011] [Citation(s) in RCA: 352] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Body temperature regulation is a fundamental homeostatic function that is governed by the central nervous system in homeothermic animals, including humans. The central thermoregulatory system also functions for host defense from invading pathogens by elevating body core temperature, a response known as fever. Thermoregulation and fever involve a variety of involuntary effector responses, and this review summarizes the current understandings of the central circuitry mechanisms that underlie nonshivering thermogenesis in brown adipose tissue, shivering thermogenesis in skeletal muscles, thermoregulatory cardiac regulation, heat-loss regulation through cutaneous vasomotion, and ACTH release. To defend thermal homeostasis from environmental thermal challenges, feedforward thermosensory information on environmental temperature sensed by skin thermoreceptors ascends through the spinal cord and lateral parabrachial nucleus to the preoptic area (POA). The POA also receives feedback signals from local thermosensitive neurons, as well as pyrogenic signals of prostaglandin E(2) produced in response to infection. These afferent signals are integrated and affect the activity of GABAergic inhibitory projection neurons descending from the POA to the dorsomedial hypothalamus (DMH) or to the rostral medullary raphe region (rMR). Attenuation of the descending inhibition by cooling or pyrogenic signals leads to disinhibition of thermogenic neurons in the DMH and sympathetic and somatic premotor neurons in the rMR, which then drive spinal motor output mechanisms to elicit thermogenesis, tachycardia, and cutaneous vasoconstriction. Warming signals enhance the descending inhibition from the POA to inhibit the motor outputs, resulting in cutaneous vasodilation and inhibited thermogenesis. This central thermoregulatory mechanism also functions for metabolic regulation and stress-induced hyperthermia.
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Affiliation(s)
- Kazuhiro Nakamura
- Career-Path Promotion Unit for Young Life Scientists, Kyoto Univ., School of Medicine Bldg. E, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
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Nakamura K, Morrison SF. Central efferent pathways for cold-defensive and febrile shivering. J Physiol 2011; 589:3641-58. [PMID: 21610139 DOI: 10.1113/jphysiol.2011.210047] [Citation(s) in RCA: 158] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Shivering is a remarkable somatomotor thermogenic response that is controlled by brain mechanisms. We recorded EMGs in anaesthetized rats to elucidate the central neural circuitry for shivering and identified several brain regions whose thermoregulatory neurons comprise the efferent pathway driving shivering responses to skin cooling and pyrogenic stimulation. We simultaneously monitored parameters from sympathetic effectors: brown adipose tissue (BAT) temperature for non-shivering thermogenesis and arterial pressure and heart rate for cardiovascular responses. Acute skin cooling consistently increased EMG, BAT temperature and heart rate and these responses were eliminated by inhibition of neurons in the median preoptic nucleus (MnPO) with nanoinjection of muscimol. Stimulation of the MnPO evoked shivering, BAT thermogenesis and tachycardia, which were all reversed by antagonizing GABA(A) receptors in the medial preoptic area (MPO). Inhibition of neurons in the dorsomedial hypothalamus (DMH) or rostral raphe pallidus nucleus (rRPa) with muscimol or activation of 5-HT1A receptors in the rRPa with 8-OH-DPAT eliminated the shivering, BAT thermogenic, tachycardic and pressor responses evoked by skin cooling or by nanoinjection of prostaglandin (PG) E2, a pyrogenic mediator, into the MPO. These data are summarized with a schematic model in which the shivering as well as the sympathetic responses for cold defence and fever are driven by descending excitatory signalling through the DMH and the rRPa, which is under a tonic inhibitory control from a local circuit in the preoptic area. These results provide the interesting notion that, under the demand for increasing levels of heat production, parallel central efferent pathways control the somatic and sympathetic motor systems to drive thermogenesis.
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Affiliation(s)
- Kazuhiro Nakamura
- Career-Path Promotion Unit for Young Life Scientists, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
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Microdissection of neural networks by conditional reporter expression from a Brainbow herpesvirus. Proc Natl Acad Sci U S A 2011; 108:3377-82. [PMID: 21292985 DOI: 10.1073/pnas.1015033108] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Transneuronal transport of neurotropic viruses is widely used to define the organization of neural circuitry in the mature and developing nervous system. However, interconnectivity within complex circuits limits the ability of viral tracing to define connections specifically linked to a subpopulation of neurons within a network. Here we demonstrate a unique viral tracing technology that highlights connections to defined populations of neurons within a larger labeled network. This technology was accomplished by constructing a replication-competent strain of pseudorabies virus (PRV-263) that changes the profile of fluorescent reporter expression in the presence of Cre recombinase (Cre). The viral genome carries a Brainbow cassette that expresses a default red reporter in infected cells. However, in the presence of Cre, the red reporter gene is excised from the genome and expression of yellow or cyan reporters is enabled. We used PRV-263 in combination with a unique lentivirus vector that produces Cre expression in catecholamine neurons. Projection-specific infection of central circuits containing these Cre-expressing catecholamine neurons with PRV-263 resulted in Cre-mediated recombination of the PRV-263 genome and conditional expression of cyan/yellow reporters. Replication and transneuronal transport of recombined virus produced conditional reporter expression in neurons synaptically linked to the Cre-expressing catecholamine neurons. This unique technology highlights connections specific to phenotypically defined neurons within larger networks infected by retrograde transneuronal transport of virus from a defined projection target. The availability of other technologies that restrict Cre expression to defined populations of neurons indicates that this approach can be widely applied across functionally defined systems.
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Morrison SF. 2010 Carl Ludwig Distinguished Lectureship of the APS Neural Control and Autonomic Regulation Section: Central neural pathways for thermoregulatory cold defense. J Appl Physiol (1985) 2011; 110:1137-49. [PMID: 21270352 DOI: 10.1152/japplphysiol.01227.2010] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Central neural circuits orchestrate the homeostatic repertoire to maintain body temperature during environmental temperature challenges and to alter body temperature during the inflammatory response. This review summarizes the research leading to a model representing our current understanding of the neural pathways through which cutaneous thermal receptors alter thermoregulatory effectors: the cutaneous circulation for control of heat loss, and brown adipose tissue, skeletal muscle, and the heart for thermogenesis. The activation of these effectors is regulated by parallel but distinct, effector-specific core efferent pathways within the central nervous system (CNS) that share a common peripheral thermal sensory input. The thermal afferent circuit from cutaneous thermal receptors includes neurons in the spinal dorsal horn projecting to lateral parabrachial nucleus neurons that project to the medial aspect of the preoptic area. Within the preoptic area, warm-sensitive, inhibitory output neurons control heat production by reducing the discharge of thermogenesis-promoting neurons in the dorsomedial hypothalamus. The rostral ventromedial medulla, including the raphe pallidus, receives projections form the dorsomedial hypothalamus and contains spinally projecting premotor neurons that provide the excitatory drive to spinal circuits controlling the activity of thermogenic effectors. A distinct population of warm-sensitive preoptic neurons controls heat loss through an inhibitory input to raphe pallidus sympathetic premotor neurons controlling cutaneous vasoconstriction. The model proposed for central thermoregulatory control provides a platform for further understanding of the functional organization of central thermoregulation.
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Affiliation(s)
- Shaun F Morrison
- Department of Neurological Surgery, Oregon Health and Science University, Portland, Oregon 97239, USA.
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Morrison SF, Nakamura K. Central neural pathways for thermoregulation. Front Biosci (Landmark Ed) 2011; 16:74-104. [PMID: 21196160 DOI: 10.2741/3677] [Citation(s) in RCA: 420] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Central neural circuits orchestrate a homeostatic repertoire to maintain body temperature during environmental temperature challenges and to alter body temperature during the inflammatory response. This review summarizes the functional organization of the neural pathways through which cutaneous thermal receptors alter thermoregulatory effectors: the cutaneous circulation for heat loss, the brown adipose tissue, skeletal muscle and heart for thermogenesis and species-dependent mechanisms (sweating, panting and saliva spreading) for evaporative heat loss. These effectors are regulated by parallel but distinct, effector-specific neural pathways that share a common peripheral thermal sensory input. The thermal afferent circuits include cutaneous thermal receptors, spinal dorsal horn neurons and lateral parabrachial nucleus neurons projecting to the preoptic area to influence warm-sensitive, inhibitory output neurons which control thermogenesis-promoting neurons in the dorsomedial hypothalamus that project to premotor neurons in the rostral ventromedial medulla, including the raphe pallidus, that descend to provide the excitation necessary to drive thermogenic thermal effectors. A distinct population of warm-sensitive preoptic neurons controls heat loss through an inhibitory input to raphe pallidus neurons controlling cutaneous vasoconstriction.
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Affiliation(s)
- Shaun F Morrison
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA.
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26
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Rigaud M, Gemes G, Abram SE, Dean C, Hopp FA, Stucky CL, Eastwood D, Tarima S, Seagard J, Hogan QH. Pain tests provoke modality-specific cardiovascular responses in awake, unrestrained rats. Pain 2010; 152:274-284. [PMID: 20943317 DOI: 10.1016/j.pain.2010.09.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Revised: 08/12/2010] [Accepted: 09/09/2010] [Indexed: 11/30/2022]
Abstract
Nociception modulates heart rate (HR) and mean arterial pressure (MAP), suggesting their use of HR and MAP as indicators of pain in animals. We explored this with telemetric recording in unrestrained control and neuropathic (spinal nerve ligation) rats. Plantar stimulation was performed emulating techniques commonly used to measure pain, specifically brush stroke, von Frey fiber application, noxious pin stimulation, acetone for cooling, and radiant heating, while recording MAP, HR, and specific evoked somatomotor behaviors (none; simple withdrawal; or sustained lifting, shaking, and grooming representing hyperalgesia). Pin produced elevations in both HR and MAP, and greater responses accompanied hyperalgesia behavior compared to simple withdrawal. Von Frey stimulation depressed MAP, and increased HR only when stimulation produced hyperalgesia behavior, suggesting that minimal nociception occurs without this behavior. Brush increased MAP even when no movement was evoked. Cold elevated both HR and MAP whether or not there was withdrawal, but MAP increased more when withdrawal was triggered. Heating, consistently depressed HR and MAP, independent of behavior. Other than a greater HR response to pin in animals made hyperalgesic by injury, cardiovascular events evoked by stimulation did not differ between control and neuropathic animals. We conclude that (a) thermoregulation rather than pain may dominate responses to heat and cooling stimuli; (b) brush and cooling stimuli may be perceived and produce cardiovascular activation without nocifensive withdrawal; (c) sensations that produce hyperalgesia behavior are accompanied by greater cardiovascular activation than those producing simple withdrawal; and (d) von Frey stimulation lacks cardiovascular evidence of nociception except when hyperalgesia behavior is evoked.
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Affiliation(s)
- Marcel Rigaud
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, USA Department of Cell Biology, Medical College of Wisconsin, WI, USA Biostatistics Consulting Service, Department of Population Health, Division of Biostatistics, Medical College of Wisconsin, WI, USA Department of Population Health, Division of Biostatistics, Medical College of Wisconsin, WI, USA Department of Anesthesiology and Intensive Care Medicine, Medical University of Graz, Graz, Austria Department of Anesthesiology, Zablocki VA Medical Center, Milwaukee, WI, USA
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The modulatory effects of rostral ventromedial medulla on air-puff evoked microarousals in rats. Behav Brain Res 2010; 215:156-9. [PMID: 20621127 DOI: 10.1016/j.bbr.2010.07.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 06/21/2010] [Accepted: 07/02/2010] [Indexed: 12/26/2022]
Abstract
This study tested whether the duration of microarousals from sleep evoked by innocuous air-puff is affected by intra-RVM administration of neurotensin and bicuculline, pharmacological manipulations that affect on and off cell activity. Air-puff evoked microarousal duration was unaffected by 0.05ng neurotensin, but decreased by 502ng neurotensin, and 5 and 50ng bicuculline. These results suggest a putative role for off cells in protecting sleep from interruption by non-noxious stimuli.
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Hellman KM, Mendelson SJ, Mendez-Duarte MA, Russell JL, Mason P. Opioid microinjection into raphe magnus modulates cardiorespiratory function in mice and rats. Am J Physiol Regul Integr Comp Physiol 2009; 297:R1400-8. [PMID: 19710394 DOI: 10.1152/ajpregu.00140.2009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The raphe magnus (RM) participates in opioid analgesia and contains pain-modulatory neurons with respiration-related discharge. Here, we asked whether RM contributes to respiratory depression, the most prevalent lethal effect of opioids. To investigate whether opioidergic transmission in RM produces respiratory depression, we microinjected a mu-opioid receptor agonist, DAMGO, or morphine into the RM of awake rodents. In mice, opioid microinjection produced sustained decreases in respiratory rate (170 to 120 breaths/min), as well as heart rate (520 to 400 beats/min). Respiratory sinus arrhythmia, indicative of enhanced parasympathetic activity, was prevalent in mice receiving DAMGO microinjection. We performed similar experiments in rats but observed no changes in breathing rate or heart rate. Both rats and mice experienced significantly more episodes of bradypnea, indicative of impaired respiratory drive, after opioid microinjection. During spontaneous arousals, rats showed less tachycardia after opioid microinjection than before microinjection, suggestive of an attenuated sympathetic tone. Thus, activation of opioidergic signaling within RM produces effects beyond analgesia, including the unwanted destabilization of cardiorespiratory function. These adverse effects on homeostasis consequent to opioid microinjection imply a role for RM in regulating the balance of sympathetic and parasympathetic tone.
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Affiliation(s)
- Kevin M Hellman
- Department of Neurobiology and 2Committee on Neurobiology, University of Chicago, Chicago, Illinois 60637, USA
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Abulafia R, Zalkind V, Devor M. Cerebral activity during the anesthesia-like state induced by mesopontine microinjection of pentobarbital. J Neurosci 2009; 29:7053-64. [PMID: 19474332 PMCID: PMC6665580 DOI: 10.1523/jneurosci.1357-08.2009] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2008] [Revised: 04/07/2009] [Accepted: 04/22/2009] [Indexed: 11/21/2022] Open
Abstract
Microinjection of pentobarbital into a restricted region of rat brainstem, the mesopontine tegmental anesthesia area (MPTA), induces a reversible anesthesia-like state characterized by loss of the righting reflex, atonia, antinociception, and loss of consciousness as assessed by electroencephalogram synchronization. We examined cerebral activity during this state using FOS expression as a marker. Animals were anesthetized for 50 min with a series of intracerebral microinjections of pentobarbital or with systemic pentobarbital and intracerebral microinjections of vehicle. FOS expression was compared with that in awake animals microinjected with vehicle. Neural activity was suppressed throughout the cortex whether anesthesia was induced by systemic or MPTA routes. Changes were less consistent subcortically. In the zona incerta and the nucleus raphe pallidus, expression was strongly suppressed during systemic anesthesia, but only mildly during MPTA-induced anesthesia. Dissociation was seen in the tuberomammillary nucleus where suppression occurred during systemic-induced anesthesia only, and in the lateral habenular nucleus where activity was markedly increased during systemic-induced anesthesia but not following intracerebral microinjection. Several subcortical nuclei previously associated with cerebral arousal were not affected. In the MPTA itself FOS expression was suppressed during systemic anesthesia. Differences in the pattern of brain activity in the two modes of anesthesia are consistent with the possibility that anesthetic endpoints might be achieved by alternative mechanisms: direct drug action for systemic anesthesia or via ascending pathways for MPTA-induced anesthesia. However, it is also possible that systemically administered agents induce anesthesia, at least in part, by a primary action in the MPTA with cortical inhibition occurring secondarily.
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Affiliation(s)
- Ruth Abulafia
- Department of Cell and Animal Biology, Institute of Life Sciences and Center for Research on Pain, Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Vladimir Zalkind
- Department of Cell and Animal Biology, Institute of Life Sciences and Center for Research on Pain, Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Marshall Devor
- Department of Cell and Animal Biology, Institute of Life Sciences and Center for Research on Pain, Hebrew University of Jerusalem, Jerusalem 91904, Israel
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Su CK, Ho CM, Kuo HH, Wen YC, Chai CY. Sympathetic-correlated c-Fos expression in the neonatal rat spinal cord in vitro. J Biomed Sci 2009; 16:44. [PMID: 19409080 PMCID: PMC2687431 DOI: 10.1186/1423-0127-16-44] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Accepted: 05/01/2009] [Indexed: 02/07/2023] Open
Abstract
An isolated thoracic spinal cord of the neonatal rat in vitro spontaneously generates sympathetic nerve discharge (SND) at ~25 degrees C, but it fails in SND genesis at < or = 10 degrees C. Basal levels of the c-Fos expression in the spinal cords incubated at < or = 10 degrees C and ~25 degrees C were compared to determine the anatomical substrates that might participate in SND genesis. Cells that exhibited c-Fos immunoreactivity were virtually absent in the spinal cords incubated at < or = 10 degrees C. However, in the spinal cords incubated at ~25 degrees C, c-Fos-positive cells were found in the dorsal laminae, the white matter, lamina X, and the intermediolateral cell column (IML). Cell identities were verified by double labeling of c-Fos with neuron-specific nuclear protein (NeuN), glial fibrillary acidic protein (GFAP), or choline acetyltransferase (ChAT). The c-Fos-positive cells distributed in the white matter and lamina X were NeuN-negative or GFAP-positive and were glial cells. Endogenously active neurons showing c-Fos and NeuN double labeling were scattered in the dorsal laminae and concentrated in the IML. Double labeling of c-Fos and ChAT confirmed the presence of active sympathetic preganglionic neurons (SPNs) in the IML. Suppression of SND genesis by tetrodotoxin (TTX) or mecamylamine (MECA, nicotinic receptor blocker) almost abolished c-Fos expression in dorsal laminae, but only mildly affected c-Fos expression in the SPNs. Therefore, c-Fos expression in some SPNs does not require synaptic activation. Our results suggest that spinal SND genesis is initiated from some spontaneously active SPNs, which are capable of TTX- or MECA-resistant c-Fos expression.
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Affiliation(s)
- Chun-Kuei Su
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, Republic of China
| | - Chiu-Ming Ho
- Department of Anesthesiology, Taipei Veterans General Hospital and National Yang-Ming University, Taipei 112, Taiwan, Republic of China
| | - Hsiao-Hui Kuo
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, Republic of China
- Department of Anesthesiology, Taipei Veterans General Hospital and National Yang-Ming University, Taipei 112, Taiwan, Republic of China
| | - Yu-Chuan Wen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, Republic of China
| | - Chok-Yung Chai
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan, Republic of China
- Department of Physiology and Biophysics, National Defense Medical Center, Taipei 114, Taiwan, Republic of China
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31
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Affiliation(s)
- Adnan I. Qureshi
- From the Zeenat Qureshi Stroke Research Center, University of Minnesota, Minneapolis
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Nociceptive behavior in animal models for peripheral neuropathy: spinal and supraspinal mechanisms. Prog Neurobiol 2008; 86:22-47. [PMID: 18602968 DOI: 10.1016/j.pneurobio.2008.06.002] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Revised: 04/08/2008] [Accepted: 06/11/2008] [Indexed: 02/01/2023]
Abstract
Since the initial description by Wall [Wall, P.D., 1967. The laminar organization of dorsal horn and effects of descending impulses. J. Neurophysiol. 188, 403-423] of tonic descending inhibitory control of dorsal horn neurons, several studies have aimed to characterize the role of various brain centers in the control of nociceptive input to the spinal cord. The role of brainstem centers in pain inhibition has been well documented over the past four decades. Lesion to peripheral nerves results in hypersensitivity to mild tactile or cold stimuli (allodynia) and exaggerated response to nociceptive stimuli (hyperalgesia), both considered as cardinal signs of neuropathic pain. The increased interest in animal models for peripheral neuropathy has raised several questions concerning the rostral conduction of the neuropathic manifestations and the role of supraspinal centers, especially brainstem, in the inhibitory control or in the abnormal contribution to the maintenance and facilitation of neuropathic-like behavior. This review aims to summarize the data on the ascending and descending modulation of neuropathic manifestations and discusses the recent experimental data on the role of supraspinal centers in the control of neuropathic pain. In particular, the review emphasizes the importance of the reciprocal interconnections between the analgesic areas of the brainstem and the pain-related areas of the forebrain. The latter includes the cerebral limbic areas, the prefrontal cortex, the intralaminar thalamus and the hypothalamus and play a critical role in the control of pain considered as part of an integrated behavior related to emotions and various homeostatic regulations. We finally speculate that neuropathic pain, like extrapyramidal motor syndromes, reflects a disorder in the processing of somatosensory information.
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Vianna D, Allen C, Carrive P. Cardiovascular and behavioral responses to conditioned fear after medullary raphe neuronal blockade. Neuroscience 2008; 153:1344-53. [DOI: 10.1016/j.neuroscience.2008.03.033] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2007] [Revised: 02/22/2008] [Accepted: 03/12/2008] [Indexed: 11/25/2022]
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Abstract
Thermogenesis, the production of heat energy, is an essential component of the homeostatic repertoire to maintain body temperature in mammals and birds during the challenge of low environmental temperature and plays a key role in elevating body temperature during the febrile response to infection. The primary sources of neurally regulated metabolic heat production are mitochondrial oxidation in brown adipose tissue, increases in heart rate and shivering in skeletal muscle. Thermogenesis is regulated in each of these tissues by parallel networks in the central nervous system, which respond to feedforward afferent signals from cutaneous and core body thermoreceptors and to feedback signals from brain thermosensitive neurons to activate the appropriate sympathetic and somatic efferents. This review summarizes the research leading to a model of the feedforward reflex pathway through which environmental cold stimulates thermogenesis and discusses the influence on this thermoregulatory network of the pyrogenic mediator, prostaglandin E(2), to increase body temperature. The cold thermal afferent circuit from cutaneous thermal receptors ascends via second-order thermosensory neurons in the dorsal horn of the spinal cord to activate neurons in the lateral parabrachial nucleus, which drive GABAergic interneurons in the preoptic area to inhibit warm-sensitive, inhibitory output neurons of the preoptic area. The resulting disinhibition of thermogenesis-promoting neurons in the dorsomedial hypothalamus and possibly of sympathetic and somatic premotor neurons in the rostral ventromedial medulla, including the raphe pallidus, activates excitatory inputs to spinal sympathetic and somatic motor circuits to drive thermogenesis.
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Affiliation(s)
- Shaun F Morrison
- Neurological Sciences Institute, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA.
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35
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Verner TA, Pilowsky PM, Goodchild AK. Retrograde projections to a discrete apneic site in the midline medulla oblongata of the rat. Brain Res 2008; 1208:128-36. [DOI: 10.1016/j.brainres.2008.02.028] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2007] [Revised: 02/10/2008] [Accepted: 02/13/2008] [Indexed: 11/28/2022]
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36
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Organization of brain somatomotor-sympathetic circuits. Exp Brain Res 2008; 187:1-16. [PMID: 18369609 DOI: 10.1007/s00221-008-1337-5] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Accepted: 02/27/2008] [Indexed: 10/22/2022]
Abstract
Numerous physiological and emotionally motivated behaviors require concomitant activation of somatomotor and sympathetic efferents. Likewise, adaptive and maladaptive responses to stress are often characterized by simultaneous recruitment of these efferent systems. This review describes recent literature that outlines the organization of somatomotor-sympathetic circuitry in the rat. These circuits were delineated by employing recombinant pseudorabies (PRV) viral vectors as retrograde trans-synaptic tract tracers. In these studies PRV-152, a strain that expresses enhanced green fluorescent protein, was injected into sympathectomized hindlimb muscle, while PRV-BaBlu, which expresses beta-galactosidase, was injected into the adrenal gland in the same animals. Immunofluorescent methods were then used to determine the presence of putative dual-function neurons that were infected with both viral strains. These somatomotor-sympathetic neurons (SMSNs) were detected in a number of brain regions. However, the most prominent nodes in this circuitry included the paraventricular, dorsomedial, and lateral nuclei of the hypothalamus, ventrolateral periaqueductal grey and ventromedial medulla. Phenotypic studies revealed subsets of SMSNs to be capable of synthesizing serotonin, or to contain neuroactive peptides vasopressin, oxytocin, orexins, or melanin-concentrating hormone. Based on these data and the results of studies employing monosynaptic tracers a central somatomotor-sympathetic circuit is proposed. This circuitry is likely recruited in diverse situations, including stress responses, cold defense, exercise and sleep. Furthermore, activation of specific classes of SMSNs likely shapes distinct stress-coping strategies. Dysregulation in the organization and function of this circuit may also contribute to the expression of physical symptoms of affective disorders, such as major depression, anxiety and panic.
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Hellman KM, Brink TS, Mason P. Activity of murine raphe magnus cells predicts tachypnea and on-going nociceptive responsiveness. J Neurophysiol 2007; 98:3121-33. [PMID: 17913977 PMCID: PMC3759357 DOI: 10.1152/jn.00904.2007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In rats, opioids produce analgesia in large part by their effects on two cell populations in the medullary raphe magnus (RM). To extend our mechanistic understanding of opioid analgesia to the genetically tractable mouse, we characterized behavioral reactions and RM neural responses to opioid administration. d-Ala(2), N-Me-Phe(4)-Gly(5)ol-enkephalin, a mu-opioid receptor agonist, microinjected into the murine RM produced cardiorespiratory depression and reduced slow wave electroencephalographic activity as well as increased the noxious heat-evoked withdrawal latencies. As in rat, RM cell types that were excited and inhibited by noxious stimuli, termed on and off cells, respectively, were observed in mice. However, in contrast to findings in rat, opioid doses that suppressed withdrawals did not alter the background discharge rate of murine on and off cells, suggesting that the cellular mechanisms by which the murine RM generates opioid analgesia are substantially different from those in rats. Murine on cell discharge did not predict the latency or magnitude of an ensuing withdrawal but did correlate to the magnitude and latency of concurrent withdrawals. Although opioids failed to alter the background discharge of on and off cells, they reduced the responses of RM neurons to noxious stimulation, further evidence that RM modulates on-going withdrawals. In characterizing the role of RM in respiratory modulation, we found that on cells burst and off cells paused during tachypneic events. The effects of opioids in the murine RM on homeostasis and the association of on and off cell discharge with tachypnea corroborate roles for opioid signaling in RM beyond analgesia.
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Affiliation(s)
- Kevin M. Hellman
- Department of Neurobiology, University of Chicago, MC 0928, 947 East 58th St., Chicago, IL 60637
| | - Thaddeus S. Brink
- Committee on Neurobiology, University of Chicago, MC 0928, 947 East 58th St., Chicago, IL 60637
| | - Peggy Mason
- Department of Neurobiology, University of Chicago, MC 0928, 947 East 58th St., Chicago, IL 60637
- Committee on Neurobiology, University of Chicago, MC 0928, 947 East 58th St., Chicago, IL 60637
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38
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Mason P, Gao K, Genzen JR. Serotonergic raphe magnus cell discharge reflects ongoing autonomic and respiratory activities. J Neurophysiol 2007; 98:1919-27. [PMID: 17715191 PMCID: PMC3759355 DOI: 10.1152/jn.00813.2007] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Serotonergic cells are located in a restricted number of brain stem nuclei, send projections to virtually all parts of the CNS, and are critical to normal brain function. They discharge tonically at a rate modulated by the sleep-wake cycle and, in the case of medullary serotonergic cells in raphe magnus and the adjacent reticular formation (RM), are excited by cold challenge. Yet, beyond behavioral state and cold, endogenous factors that influence serotonergic cell discharge remain largely mysterious. The present study in the anesthetized rat investigated predictors of serotonergic RM cell discharge by testing whether cell discharge correlated to three rhythms observed in blood pressure recordings that averaged >30 min in length. A very slow frequency rhythm with a period of minutes, a respiratory rhythm, and a cardiac rhythm were derived from the blood pressure recording. Cross-correlations between each of the derived rhythms and cell activity revealed that the discharge of 38 of the 40 serotonergic cells studied was significantly correlated to the very slow and/or respiratory rhythms. Very few serotonergic cells discharged in relation to the cardiac cycle and those that did, did so weakly. The correlations between serotonergic cell discharge and the slow and respiratory rhythms cannot arise from baroreceptive input. Instead we hypothesize that they are by-products of ongoing adjustments to homeostatic functions that happen to alter blood pressure. Thus serotonergic RM cells integrate information about multiple homeostatic activities and challenges and can consequently modulate spinal processes according to the most pressing need of the organism.
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Affiliation(s)
- Peggy Mason
- Department of Neurobiology, University of Chicago, Chicago, IL 60637, USA.
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Reiner K, Sukhotinsky I, Devor M. Mesopontine tegmental anesthesia area projects independently to the rostromedial medulla and to the spinal cord. Neuroscience 2007; 146:1355-70. [PMID: 17395384 DOI: 10.1016/j.neuroscience.2007.02.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2006] [Revised: 01/22/2007] [Accepted: 02/15/2007] [Indexed: 11/27/2022]
Abstract
General anesthetics are presumed to act in a distributed manner throughout the CNS. However, we found that microinjection of GABAA-receptor (GABAA-R) active anesthetics into a restricted locus in the rat brainstem, the mesopontine tegmental anesthesia area (MPTA), rapidly induces a reversible anesthesia-like state characterized by suppressed locomotion, atonia, anti-nociception and loss of consciousness. GABA-sensitive neurons in the MPTA may therefore have powerful control over major aspects of brain and spinal function. Tracer studies have shown that the MPTA projects to the rostromedial medulla, an important reticulospinal relay for pain modulation and motor control. It also projects directly to the spinal cord. But do individual MPTA neurons project to one or to both targets? We microinjected fluorogold into the rostromedial medulla and cholera toxin b-subunit into the spinal cord, or vice versa. Neurons that were double-labeled, and hence project to both targets, were intermingled with single-labeled neurons within the MPTA, and comprised only 11.5% of the total. MPTA neurons that project directly to the spinal cord were larger, on average, than those projecting to the rostromedial medulla, differed in shape, and were much more likely to express GABAA-alpha1Rs as assessed by receptor alpha-1 subunit immunoreactivity (51.4% vs. 18.9%). Thus, for the most part, separate and morphologically distinct populations of MPTA neurons project to the rostromedial medulla and to the spinal cord. Either or both may be involved in the modulation of nociception and the generation of atonia during the MPTA-induced anesthesia-like state.
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Affiliation(s)
- K Reiner
- Department of Cell and Animal Biology, Institute of Life Sciences, and Center for Research on Pain, Hebrew University of Jerusalem, Jerusalem 91904, Israel
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40
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Kerman IA, Shabrang C, Taylor L, Akil H, Watson SJ. Relationship of presympathetic-premotor neurons to the serotonergic transmitter system in the rat brainstem. J Comp Neurol 2007; 499:882-96. [PMID: 17072838 DOI: 10.1002/cne.21129] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Numerous physiological conditions and emotionally motivated behaviors require concomitant activation of somatomotor and sympathetic efferents. Using a virally mediated retrograde transsynaptic tract-tracing approach, we have previously determined locations of presympathetic-premotor neurons (PSPMNs) in the rat brainstem. These putative dual-function neurons send projections to somatomotor and sympathetic targets and likely participate in sympatho-somatomotor integration. A significant portion of these neurons is found within brainstem areas known to contain serotonergic neurons. Thus, we hypothesized that some of the PSPMNs utilize serotonin as their neurotransmitter. To test this hypothesis we first produced an antibody against TPH2, a brain-specific isoform of tryptophan hydroxylase (serotonin synthetic enzyme). We identified PSPMNs by using recombinant strains of the pseudorabies virus (PRV) for transsynaptic tract-tracing. PRV-152, a strain that expresses enhanced green fluorescent protein, was injected into sympathectomized gastrocnemius muscle, while PRV-BaBlu, which expresses beta-galactosidase, was injected into the adrenal gland in the same animals. Using immunofluorescent methods we determined whether coinfected neurons expressed TPH2. Our findings demonstrate that TPH2-positive PSPMNs are present at different rostrocaudal levels of the brainstem. Just over half of them are found at the pontomedullary junction within raphe obscurus, raphe magnus, and gigantocellular nucleus pars alpha. These cells may play a role in mediating responses to acute pain stimuli and/or participate in the central control of exercise. Overactivity of these serotonergic sympatho-somatomotor circuits may also play a role in the pathophysiology of serotonin syndrome.
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Affiliation(s)
- Ilan A Kerman
- Molecular and Behavioral Neuroscience Institute, University of Michigan, Ann Arbor, Michigan 48109, USA.
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41
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Morélot-Panzini C, Demoule A, Straus C, Zelter M, Derenne JP, Willer JC, Similowski T. Dyspnea as a Noxious Sensation: Inspiratory Threshold Loading May Trigger Diffuse Noxious Inhibitory Controls in Humans. J Neurophysiol 2007; 97:1396-404. [PMID: 16870842 DOI: 10.1152/jn.00116.2006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dyspnea, a leading respiratory symptom, shares many clinical, physiological, and psychological features with pain. Both activate similar brain areas. The neural mechanisms of dyspnea are less well described than those of pain. The present research tested the hypothesis of common pathways between the two sensations. Six healthy men (age 30–40 yr) were studied. The spinal nociceptive flexion reflex (RIII) was first established in response to electrical sural stimulation. Dyspnea was then induced through inspiratory threshold loading, forcing the subjects to develop 70% of their maximal inspiratory pressure to inhale. This led to progressive inhibition of the RIII reflex that reached 50 ± 12% during the fifth minute of loading ( P < 0.001), was correlated to the intensity of the self-evaluated respiratory discomfort, and had recovered 5 min after removal of the load. The myotatic H-reflex was not inhibited by inspiratory loading, arguing against postsynaptic alpha motoneuron inhibition. Dyspnea, like pain, thus induced counterirritation, possibly indicating a C-fiber stimulation and activation of diffuse noxious inhibitory descending controls known to project onto spinal dorsal horn wide dynamic range neurons. This confirms the noxious nature of certain types of breathlessness, thus opening new physiological and perhaps therapeutic perspectives.
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Affiliation(s)
- Capucine Morélot-Panzini
- Laboratoire de Physiopathologie Respiratoire, Service de Pneumologie et de Réanimation, Groupe Hospitalier Pitié Salpétrière, 47-83 boulevard de l'Hôpital, 75651 Paris Cedex 13, France
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42
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Sukhotinsky I, Reiner K, Govrin-Lippmann R, Belenky M, Lu J, Hopkins DA, Saper CB, Devor M. Projections from the mesopontine tegmental anesthesia area to regions involved in pain modulation. J Chem Neuroanat 2006; 32:159-78. [PMID: 17049433 DOI: 10.1016/j.jchemneu.2006.08.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Revised: 08/25/2006] [Accepted: 08/30/2006] [Indexed: 11/19/2022]
Abstract
Pentobarbital microinjected into a restricted locus in the upper brainstem induces a general anesthesia-like state characterized by atonia, loss of consciousness, and pain suppression as assessed by loss of nocifensive response to noxious stimuli. This locus is the mesopontine tegmental anesthesia area (MPTA). Although anesthetic agents directly influence spinal cord nociceptive processing, antinociception during intracerebral microinjection indicates that they can also act supraspinally. Using neuroanatomical tracing methods we show that the MPTA has multiple descending projections to brainstem and spinal areas associated with pain modulation. Most prominent is a massive projection to the rostromedial medulla, a nodal region for descending pain modulation. Together with the periaqueductal gray (PAG), the MPTA is the major mesopontine input to this region. Less dense projections target the PAG, the locus coeruleus and pericoerulear areas, and dorsal and ventral reticular nuclei of the caudal medulla. The MPTA also has modest direct projections to the trigeminal nuclear complex and to superficial layers of the dorsal horn. Double anterograde and retrograde labeling at the light and electron microscopic levels shows that MPTA neurons with descending projections synapse directly on spinally projecting cells of rostromedial medulla. The prominence of the MPTA's projection to the rostromedial medulla suggests that, like the PAG, it may exert antinociceptive actions via this bulbospinal relay.
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Affiliation(s)
- I Sukhotinsky
- Department of Cell and Animal Biology, Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel.
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43
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Abstract
Recent evidence suggests that neurons in the medullary raphe are critical to the activation of brown adipose tissue (BAT), the major source of nonshivering heat production in the rat. Yet it is unclear which medullary raphe cells participate in cold defense and how participating cells contribute to BAT activation. Therefore, we recorded extracellularly from raphe cells during three thermoregulatory challenges that evoked an increase in BAT temperature in anesthetized rats: central cold, ambient cold, or intracerebroventricular prostaglandin E2 (PGE2) injection. Physiologically identified serotonergic (p5HT) cell discharge increased in response to cold or PGE2 administration and was positively correlated with BAT temperature. However, none of the 147 physiologically identified non-serotonergic (non-p5HT) cells recorded responded to thermoregulatory challenges that evoked an increase in BAT temperature. To test for modulation of BAT activation by non-p5HT cells that are either excited (ON cells) or inhibited (OFF cells) by noxious cutaneous stimulation, noxious stimuli were applied during evoked BAT temperature increases. Noxious stimulation suppressed BAT activation, suggesting that cells inhibited by noxious stimulation facilitate spinal circuits controlling BAT. To test whether medullary OFF cells modulate BAT activity, the mu-opiate receptor agonist (d-Ala2, N-Me-Phe4, Gly-ol5)-enkephalin (DAMGO) was microinjected into the raphe magnus, a manipulation that selectively activates OFF cells. DAMGO microinjection blocked noxious stimulation-evoked suppression of PGE2-induced BAT temperature increases. Thus, both p5HT and non-p5HT OFF cells in the medullary raphe facilitate BAT activation in response to cold challenge or pyrogen.
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Abstract
The midbrain periaqueductal gray (PAG) and ventromedial medulla (VMM) are generally viewed as the core of an endogenous descending modulatory system. However, available data demonstrate that PAG and VMM do not specifically target nociceptive transmission and that activation of either structure affects numerous homeostatic physiological processes. Pseudorabies virus (PRV) is a useful tracer that is retrogradely and transynaptically transported. PRV injections into homeostatic effector organs invariably label VMM neurons, both serotonergic and nonserotonergic. Studies in anesthetized rats have implicated two types of nonserotonergic VMM neurons in nociceptive modulation: ON cells are thought to facilitate nociception and OFF cells to inhibit nociception. Yet, in the unanesthetized animal, the discharge of VMM neurons changes in response to innocuous stimuli and during situations unrelated to nociception. In particular, VMM cells appear to modulate the timing of micturition, with ON cells promoting the initiation of voiding and OFF cells promoting urine storage. VMM cells also modulate sensory transmission. During both micturition and sleep, OFF cells discharge and sensory responsiveness is depressed. In sum, the VMM is hypothesized to modulate spinal sensory, autonomic, and motor circuits in order to maintain homeostasis.
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Affiliation(s)
- Peggy Mason
- Department of Neurobiology, Pharmacology & Physiology and Committee on Neurobiology, University of Chicago, Chicago, Illinois 60637, USA.
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Abstract
A pathway from the midbrain periaqueductal gray (PAG) through the ventromedial medulla (VMM) to the dorsal horn constitutes a putative endogenous nociceptive modulatory system. Yet activation of neurons in both PAG and VMM changes the responses of dorsal horn cells to non-noxious stimuli and elicits motor and autonomic reactions that are not directly related to nociception. Activation of mu-opioid receptors in VMM and PAG also modifies processes in addition to nociceptive transmission. The descending projections of VMM neurons are not specific to nociception as VMM projects to the spinal superficial dorsal horn where thermoreceptors as well as nociceptors terminate. In addition, experiments with pseudorabies virus demonstrate multi-synaptic pathways from VMM to sympathetic and parasympathetic target organs. VMM neurons respond to both noxious and unexpected innocuous stimuli of multiple modalities, and change their discharge during behaviors unrelated to pain such as micturition/continence and sleep/wake. In conclusion, all available evidence argues against the idea that PAG and VMM target nociception alone. Instead these brain stem sites may effect homeostatic adjustments made necessary by salient situations including but not limited to injury.
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Affiliation(s)
- Peggy Mason
- Department of Neurobiology, Pharmacology and Physiology, University of Chicago, MC 0926, 947 East 58th St., Chicago, IL 60637, USA.
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Abstract
Studies in anesthetized animals implicate nonserotonergic cells in the ventromedial medulla (VMM) in opioid modulation of nociceptive transmission but do not reveal the conditions that engage VMM cells in unanesthetized rats. The few studies of VMM cells in unanesthetized rats show that VMM cells change their discharge across the sleep-wake cycle and during active movements. Since active movements are more likely to occur during waking than sleep, state-related discharge may in fact represent movement-related discharge. In this study, we recorded the discharge of VMM neurons in unanesthetized, drug-free, freely moving rats and examined whether neuronal activity was related to wake/sleep state, to motor activity, or to both factors. Most cells (45/67) were more active during waking states than sleeping states, 1 cell was more active during sleep states, and the remaining 21 cells did not fire preferentially across the sleep-wake cycle. Most wake-active cells (36/45) showed discharge bursts during movement bursts, and 9/11 wake-active cells were excited by noxious heat and innocuous air puff stimulation. In contrast, few state-independent cells (9/21) showed movement-related bursts in discharge. These results suggest that VMM neurons modulate spinal processes during phasic motor activity.
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Affiliation(s)
- H Foo
- Department of Neurobiology, Pharmacology and Physiology, University of Chicago, 947 East 58th St., Chicago, IL 60637, USA
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